The present invention relates to fire retarding door assemblies, and, more specifically, to fire actuated latch bolt assemblies for use in connection with doors to retain the door in the door opening.
As is well known, it is extremely desirable that fire retarding doors remain firmly within the door opening during fires in order to prevent the fire from rapidly spreading to other parts of the building and/or to limit the air to support combustion in a room in which there is an active fire. To achieve this result, many building codes require that doors in commercial buildings (and in some residential structures) have a fire resistance rating which will provide an effective fire barrier for a reasonable period of time. Thus, many doors for commercial buildings are fabricated with metal skins and frames, and others utilize fire-retardant materials which will provide a lesser degree of temperature resistance.
The door frames which are conventionally employed in fire-rated structures are generally comprised of metal jambs and headers. In fire-rated installations, it is necessary that the latch assembly utilized to secure the door in its closed position and the hinge assembly for mounting the door also have a fire rating sufficient to provide the desired protection to a specified temperature for a specified time.
As is known, metal-clad doors in which the skins are welded to metal stiles and headers, the heat of a fire may result in substantial warping pressures which can cause the hinges to distort or to disengage from the jamb or door. This could open the door passage to flames and air flow.
Recently, for cosmetic applications, there has been considerable interest in utilizing hinges made of aluminum and other metals which have lower fire resistance than the ferrous metals which are conventionally employed in fire-retardant door assemblies. This is particularly true of aluminum continuous hinges which extend over substantially the entire length of the hinge side of the door to provide a unique appearance and a high strength assembly under normal conditions.
Underwriters Laboratory and other safety agencies perform a fire test in which temperatures reach at the source approximately 2000.degree. F. At this temperature, a continuous hinge made from aluminum would quickly melt since the melting temperature of most common aluminum alloys is 1200.degree. F. Brass butt hinges start to melt at approximately 1600.degree. F. Both of these types of hinges will distort at lower temperatures.
It is an object of the present invention to provide a novel fire-retarding door assembly employing fire-actuated latching devices which will serve to retain a door firmly within the door opening during a fire.
It is also an object to provide such a door assembly which will function to seal the door opening even if the hinge assembly loses its strength due to exposure to high temperatures.
Another object is to provide such an assembly in which the fire-actuated latching device may be readily fabricated and installed.
A further object is to provide such fire-actuated latching devices for use in fire-retarding door assemblies.